Apparatus for driving bolts into masonry, structural parts and the like



Aug. 31, 1965 K DIE Filed April 11, 1962 APPARATUS FOR DRIVING B-OLTS INTO MASONRY, STRUCTURAL PARTS AND THE LIKE 2 Sheets-Sheet l K. DIEHL 3,203,609 APPARATUS FOR DRIVING BOLTS INTO MASONRY, STRUCTURAL Aug. 31, 1965 PARTS AND THE LIKE 2 Sheets-Sheet 2 Filed April 11, 1962 f E VZ, f V

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United States Patent O 3,203,609 APPARATUS FOR DRIVING BOLTS INTO MASON- RY, STRUCTURAL PARTS AND THE LIKE Karl Diehl, Wuppertal-Elberfeld, Germany, assignor to 'CM1 Bauer, Wuppertal-Cronenberg Germany, a rm Filed Apr. 11, 1962, Ser. '.No. 186,746 Claims priority, application Germany, Apr. 13, 1961, B 62,126; .lune 22, I1961, B 62,996 9 Claims. (Cl. 227-8) The invention has for its object to improve apparatus for driving bolts into masonry and structural parts or the like of the type described at the outset and particularly to eliminate the objections mentioned in connection with the known forms of construction.

This object is attained according to the invention by the provision of an apparatus for driving bolts into masonry, structural parts and the like which comprises a housing, a piston cooperating with a bolt slidable in the interior of said housing, a cartridge holder also accommodated in said housing outside the range of action of the tiring mechanism of the apparatus when the apparatus is in unloaded state and within the range of action of said ring mechanism when the apparatus is in loaded state, the cartridge holder always assuming the same position in relation to the firing mechanism independently of the length of the bolt to be driven in.

This form of construction presents Vconsiderable advantages over the known apparatus, namely first it is no longer possible to fire into space or to lire without a bolt being inserted; then the mutual positions of the cartridge holder and consequently of the cartridge on the one hand `and the firing mechanism on the other hand are always the same independently of the length of the bolt actually to be driven in, and furthermore, any failures which might occur can easily be overcome. For example, cartridges which have not been fired can be removed in a simple manner. Another great advantage is that the dead mass of the apparatus is utilized for braking the recoil.

According to a further feature, the cartridge holder may be arranged to cooperate with an abutment shoulder when the apparatus is in loaded state, the abutment shoulder being formed by projections on the inner walls of a closing ring of the apparatus and also serves as support for springs between the closing ring and a projecting jacket.

When the apparatus is not cocked the cartridge holder is located at a distance from the abutment shoulder and consequently outside the range of action of the releasing mechanism. Only when a bolt has been inserted the length of which is immaterial, does the cartridge holder bear against the said abutment shoulder, and come within the range of action of the releasing mechanism, retaining this position independently of the length of the inserted bolt.

The apparatus may be composed of several parts which are slidable one within the other to enable the length of the apparatus to be varied. Conveniently, the apparatus may be provided with a housing slidable in a straight line in the longitudinal direction of the apparatus in relation to an outer cylinder. It is also expedient to arrange the piston so that it may pass through an inner cylinder which cooperates at one end with the outer cylinder and at the other end with the cartridge holder loaded by a spring.

According to a further suggestion, at least three bearing points may be associated with the piston irrespectively of its position.

Consequently, it is possible, as in the known apparatus, to dispense altogether with the use of an additional guiding element. Such known guiding elements are for example, discs fitted on the bolt shank.

3,2%,699 Patented Aug'. 31, 1955 In the abovedescribed form of construction of an apparatus for driving bolts into masonry or the like, this apparatus has relatively many component parts and guiding and friction surfaces. Consequently, a second form of construction is indicated in which the number of component parts is reduced. In addition it enables the cornponents to be easily taken apart, particularly the front part of the apparatus. This form of construction is characterized by a smaller number of guiding and friction surfaces. According to the invention, in this form of construction the cartridge holder may be accommodated in the inner cylinder slidable between two fixed abutments, namely an abutment shoulder and an abutment surface, the space between which abutments corresponds to the path necessary for bringing the apparatus into the releasing position.

Expediently, one abutment may be formed by the abutment shoulder of a closing ring and the other by the abutment surface of an abutment sleeve which may be clamped between the closing ring and an outer guide tube of the apparatus.

As already mentioned, the possible sliding movement of the inner cylinder is limited within the housing of the apparatus, i.e., it can only be displaced between the two xed abutments over a distance that must be covered to bring the apparatus in the releasing position.

This distance must be travelled against the resistance offered by a firing-pin spring and can only be covered when a bolt is inserted. By this construction it is prevented that the apparatus with the cartridge can be brought into firing position if no bolt presses against the bearing surface on the masonry. In other words: if the bolt is not inserted in the space provided for it in the piston the adapter sleeve cooperating therewith cannot shift and consequently the apparatus cannot be brought into the releasing position.

Further details of the invention will be explained in the following description.

Two preferred embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which:

FIG. 1 is a longitudinal section through the first embodiment of an apparatus for driving bolts into masonry or the like according to the invention, in unloaded state;

FIG. 2 is a similar view but with the apparatus in loaded or cocked state and in releasing position with the shortest type of bolt to be driven in;

FIG. 3 is a similar view but with the longest type of bolt to be driven in;

FIG. 4 is a longitudinal section through a second form of construction of an apparatus for driving bolts into madsonry, with a protecting cap and in unloaded state, an

FIG. 5 is a similar view but in loaded or cocked state, partly broken away and with the protecting cap turned through an angle of It is first mentioned that the firing mechanism does not form part of the invention. Consequently the construction of the firing mechanism (see FIG. 4) in the second form of construction is only shown to demonstrate the manner in which the apparatus operates. This firing mechanism is known per se but if necessary can be replaced by some other firing means also of known construction. Consequently, only the important parts of the firing mechanism will be explained in the following description. The firing mechanism according to FIG. 4 may also be used in the rst embodiment of the invention illustrated in FIGS. l to 3. In this case, only a slight modification in the region of a lever 39 of the tiring mechanism is necessary.'

FIG. l shows an apparatus for driving bolts into masonry, structural parts and the like according to the inice vention, which comprises a protecting cap 4 having an end face 40 which bears against an area of masonry 16 or the like into which a bolt 18 is to be driven by means of the apparatus. An outer cylinder 5 is connected with the protecting cap 4. The connection between these two parts is such that it is rigid when in use, but for example for purposes of repair and the like, the protecting cap 4 can be separated from the outer cylinder 5. For this purpose the outer cylinder 5 is formed with a shoulder 5 and a snap ring 4 located in a groove in the outer cylinder 5 engages a front portion of the cap 4 to maintain a portion of the cap in engagement with the shoulder 5. The apparatus also has a housing 6 which can be shifted in relation to the outer cylinder 5 in the manner hereinafter described. A closing ring 8 is screwed on to a screw thread 7 on the rear end of the housing 6 and has in the region of its inner walls abutment shoulders 9 which are utilized as abutments for a cartridge holder 13 in the manner hereinafter described. As shown, for example in FIG. 3, the abutment shoulders 9 leave an aperture 100 free through which part of the cartridge holder 13 projects when the apparatus is in loaded or cocked state. The abutment shoulders 9 also serve as supporting surfaces for the ends of two springs 111 and 12, the other end of the spring 111 bearing against the outer cylinder 5 and the other end of the spring 12 against the cartridge holder 13. The cartridge holder 13 4is fixed to an inner cylinder 14 which is slidably guided in the outer cylinder 5.

A piston 15 is slidable in the apparatus and has in its part facing the masonry 16 a recess 17 in which a bolt 18 to be driven in is partly accommodated. The piston 15, although actually in one piece, is composed of a number of separate sections which will be hereinafter described. First there is a front piston section 19 in which the above-mentioned recess 17 is provided for receiving part of the bolt 18. The outer surface of the piston section 19 is arranged for cooperation with guide portion 20 of reduced diameter formed in a front part of the outer cylinder 5. The piston section 19 is followed by a section 21 having a larger diameter than section 19 and being so dimensioned that it corresponds substantially to the diameter of the bore in the outer cylinder 5. A section 22 of the piston 15 being by far the longest section thereof is surrounded by the inner cylinder 14 and is reduced in diameter as compared with the section 21. Extending from the free rear end of this section 22 is another section 27 which has the smallest diameter of the whole piston 15 and engages in a correspondingly dimensioned bore 34 in the cartridge holder Y 13. This section 27 of the piston 15 only lls a portion of the bore 34 of the cartridge holder 13, as can be seen for example from FIG. l of the drawing, the remaining portion of this bore 34 being utilized for accommodating the cartridge.

Between the individual parts of the apparatus a pluarlity of packing rings 41 are tted the positions and construction of which are not explained in detail for the sake of simplicity. The largest section 21 of the piston 15 may cooperate with an abutment surface 26 which is formed by the guide portion 20 of the outer cylinder 5.

The cartridge holder 13 has, as can be seen from FIGS. 1 to 3, several transverse bores 127 which are intended to allow the escape of the gases under pressure and which communicate at their inner ends with a chamber 13' formed in the cartridge holder intermediate its ends, whereas the outer ends of bores 127 communicate with the interior of the housing 6. It is here pointed out that during forward movement of the piston 15 the transverse bores 127 will communicate with bore 34 already before the section 21 of the piston 15 strikes against the abutment surfaces 26.

The apparatus as shown in FIG. 1 is in unloaded or uncocked position and it can be seen that in this position the cartridge holder 13 is located fa rin the interior of the housing, so that it is removed from the action of a firing mechanism. It is therefore not possible to use the apparatus in this position.

FIG. 2 of the drawing shows the position of the parts after the apparatus has been charged or cocked, namely in the releasing position for the shortest ty e of bolts. In this position the apparatus has its shortest possible dimensions because the housing 6 bears directly against the rear part of the protecting cap 4. It will, however, be seen from FIG. 2 that even if the housing 6 is pressed forwardly so that the front face thereof engages the rear end of the protective cap 4, the cartridge holder 13 will still not be in a position ready for tiring as long as no bolt 18 is inserted into the recess 17 formed in the front end of the piston 15. The cartridge holder 13 can be placed in position ready for firing only after a bolt 18 is placed in the recess in the front end of the piston 15 whereby the piston is moved rearwardly with respect to the outer cylinder 5 and engages with its collar 21 the front end of the inner cylinder 14 to move the latter and the cartridge holder 13 connected thereto rearwardly with respect to the outer cylinder 5 to place the cartridge holder in its tiring position. FIG. 2 shows the shortest bolt 18 which can be used in the apparatus inserted into the recess of the piston 15 and in this case the housing 6 has to be pressed forwardly until the front of the housing engages the rear end of the protective cap 4 to bring the apparatus in tiring position after the bolt 18 has been inserted.

FIG. 3, on the other hand, shows the apparatus in a position ready for ring in which the longest bolt 1S usable in the apparatus is inserted into the recess of the front end of the piston 15. As is evident from FIG. 3, the housing 6 has in this case to be pressed forward only a very small amount in order to bring the cartridge holder 13 in the position ready for tiring.

The apparatus of the present invention can therefore be used with bolts of different lengths, but the apparatus cannot be brought into a position ready for firing without inserting a bolt in the front end of the piston 15.

An important advantage of the apparatus according to the invention also consists in that the piston is preferably guided at least three places, and independently of the position which it assumes at any time in the interior of the apparatus. Even when it has passed out of the guide 20 into the position shown in FIG. 3, it will be always guided at least at three places. When the piston 15 leaves the guide in the region of the rear part of the cartridge holder 13, its front section 19 already will have reached the guide 20. By these numerous guides a str-aight line forward movement of the piston 15 and consequently of the bolt 1S is reliably assured so that it is possible to dispense with the use of additional guides, for example the use of disks fitted on the shank of the bolt 18.

The apparatus for driving bolts into masonry or the like according to the embodiment shown in FIGS. 4 and 5 has also the protecting cap 4 with the end face 4i) which bears, when in use, against the masonry 16 or generally speaking against that structural part into which the bolt 18 is to be driven. The outer cylinder 5 is connected with the protecting cap 4. The connection between these two parts is of such type that it is rigid when in use yet the protecting cap 4 can be separated from the outer cylinder 5 for example for the purposes of repair. Preferably special tools should be used for effecting the disconnection in order to render it diicult to be taken apart by unauthorized persons. The apparatus also has the housing 6 which can be shifted relatively to the outer cylinder 5. The closing ring 8 is screwed on to the screw thread 7 on the rear end of the housing 6 and has the abutment shoulders 9 in the region of its inner walls. These shoulders 9 form an abutment for an inner cylinder 31 to be described later. The second abutment is formed by an abutment sleeve 10 which is clamped be.

tween the housing 6 and the closing ring 8 of the apparatus. As shown, for example in FIG. 4, the abutment sleeve 10 in assembled state is stationary between the two separated parts and has an abutment surface 11. The inner cylinder 31 can then be shifted only between the abutment shoulders 9 and the abutment surface 11, the relative spacing of these two abutments being such that the apparatus can be brought into the releasing position. This can however only be effected when the bolt 18 is inserted (see FIG. 5).

One end of the spring 12 bears against the abutment sleeve 10 while the other end bears against a surface of `the outer cylinder 5. The inner end face of the outer cylinder 5 can enter into operative connection with the stepped surface of the abutment sleeve 10, which then results in limiting the relative shifting movement between the outer cylinder 5 and the housing 6. In FIG. 5, these surfaces are not in contract which means that longer bolts 1S than that which is inserted can be shot with the apparatus.

The apparatus according to this embodiment is also provided with a piston 15 which is shiftable in the apparatus and has in its part facing the masonry 16 the recess 17 open at one end in which the rear end of a bolt 18 is fitted. In the example illustrated the piston 15 is shown in one piece, but it can also be composed of several parts fitted together. The piston 15 has a front piston section 19 in which the recess 17 is provided for receiving parts of the bolt 18. The outer surfaces of the piston section 19 cooperate with the guides 26 which are formed by the projecting parts of the outer cylinder 5. Following the piston section 19 is again a section 21 of larger diameter which is so dimensioned that its diameter corresponds substantially to the diameter of the bore of the outer cylinder 5. The shank-like section 22 which is by far the longest section of the piston is surrounded by the inner cylinder 31 and of smaller diameter than the section 21. The section 22 of the piston 15 has a preferably ring-shaped recess 23 in which a correspondingly shaped packing 24 is inserted. Directly adjacent the recess 23 there is a collar 25 on the piston 15 which is followed by a section 25 of reduced diameter which on its part is followed by the stepped section 27 the diameter of which is so dimensioned that it corresponds substantially to the diameter of the bore 34. A shoulder 29 formed by the stepping bears against a surface 30 of the inner cylinder 31. The diameter of the section 27 in relation to the diameter of the chamber-like space in which the section 26 of the piston 15 is accommodated, is in a ratio of about 1:25. The section 27 has an end face 28 which is lirst exposed to the propellent gases. The region of the piston 15 facing the bore 34 is subjected to the strongest stress as it will be acted upon by the hot combustion gases. The wear of this region is therefore greatest. To take this into consideration, the piston 15 may be composed of several parts in the preferred form of construction. The dividing plane is therefore preferably located behind the recess 23 because the packing 24 fitted at this point is a closing element. lf desired, the part of the piston 15 towards the bore 34 may be removed and replaced by a spare part. It is immaterial what means will be chosen for this detachable connection, but a screw or bayonet joint is suggested.

The bore 34 lof the inner cylinder 31 may be used as cartridge holder and the inner cylinder 31 preferably has a continuous collar 32 for cooperation with the abutment shoulder 9 and abutment surface 11 mentioned at the outset. When the apparatus is in the unloaded position shown in FIG. 4 of the drawings the continuous circumferential collar 32 of the inner cylinder 31 bears against the abutment surface 11 of the abutment sleeve 10 whereas in loaded state the same collar 32 bears against the abutment shoulder 9 of the closing ring 8 (see FIG. 5). It is also mentioned that the bore 34 is 6, provided in a section 33 of the inner cylinder 31 which is -of smaller diameter than the collar 32 and engages in an opening in the inner walls of the closing ring 8, not shown in detail, so that in releasing position a striker pin 35, which is adapted to cooperate in a known manner with springs not shown in detail, will be capable of acting on the cartridge.

As already mentioned, the tiring mechanism is of known construction. In the example chosen it represents a so-called breech closure having a swing element 36. The firing mechanism also has a likewise known handle 37 and a trigger 3S and iinally the lever 39 by means of which the mechanism is opened for example for inserting the cartridge.

The operations which take place during the ignition of the cartridge have already been explained at the outset. In particular, the pressure conditions were investigated which take place during the forward movements of the piston 15. Now, also the operations which take place when using a so-called breech closure as in the example chosen will be described. It is assumed that the piston 15 has moved forward already so far that the propellent gases are not only in the bore 34 but also already in a chamber 13 adjacent the bore. As the expansion of the gases progresses, the breech element 36 is lifted oif the rear end of the inner cylinder 31. The pressure still present in the cartridge holder loosens the cartridge and thus also exerts a pressure on the very large surface of the breech element 36 of the releasing mechanism.

The cooperation of all the measures described results in very extensive utilization of the cartridge energy for the driving-in operation in spite of the low driving-in speed. This is also the reason why no appreciable recoil occurs even during a necessary destruction or absorption of the greater par-t of this driving-in energy when driving into soft material.

As can be seen from FIG. 5 of the drawings, the bolt 18 is provided with a perforated disc 44 for cooperation with catches accommodated in the protecting cap 4. These catches, which will be hereinafter described, serve the purpose of preventing the bolt 18 from falling out lof the apparatus, for example when the apparatus is to be used directed downwards. There are in the protecting cap 4 two preferably diagonally opposite transverse bores 42 in each of which -a catch ball 43 or the like is accommodated so that it projects partly from the transverse bores 42 to engage with the perforated disc 44. The catches 43 are each loaded by a respective spring 45, which springs are each accommodated in one of the transverse bores 42 and bear against a respective screw plug 46. The screw plugs 46 can be removed from the protecing cap if required, for example for the purposes of repair or the like. It is likewise mentioned that the apparatus has a plurality of packings 41.

The proportion of the diameter of the cartridge holder in relation to the diameter of the neighbouring chamber 13 is in this form of construction given as 1:2.5. In many cases this ratio can be varied, but should be within the limits of 1:1.5 to 1:5.

As already mentioned the forms of construction illustrated are only given by way of example and the invention is not restricted thereto. On the contrary many other forms of construction and applications are possible. In particular, the apparatus, diifering from the example shown, may be equipped with some other known releasing mechanism. While in the example illustrated the packing ring coordinated to the piston is made from elastic material, it can, according to another suggestion, be made of steel. Such a form of construction has the advantage of a longer service life.

I claim:

1. An apparatus for driving bolts into masonry or the like comprising, in combination, a housing having 'a rear end adapted to carry a firing mechanism; cylinder means having a front end and a rear portion facing the rear end of said housing yand forming a cartridge holder, said cylinder means being slidably guided in said housing `between a forward idle position and a cocked position in which said cartridge holder is located at said rear end of said housing ready to cooperate with the firing mechanism; spring means engaging said cylinder means and biased so as to yieldably maintain said cylinder means in said idle position so as to prevent movement of said cylinder means `to said cocked position in the absence of a bolt in said front end portion of said cylinder means; and a piston slidably guided in said cylinder means, said piston having a front end adapted to engage a bolt to be driven by said apparatus and said piston having a shoulder face engaging a corresponding shoulder face on said cylinder means so as to move said cylinder means from said idle to said cocked position upon insertion of a bol-t int-o said front end of said cylinder means in engagement with said `front end of said piston and upon exerting forward pressure on said housing.

2. An apparatus for driving bolts into masonry or 'the like comprising, in combination, a housing having a rear end adapted to carry a tiring mechanism; cylinder means comprising an outer cylinder having a front end and ibeing slidably guided in said housing between an extended position and a rearwardly retracted position, an inner cylinder having a rear portion facing said rear end of said housing, and a cartridge holder connected to said rear portion of said inner cylinder, said inner cylinder being slidably guided in said outer cylinder :between a forward idle position and a cocked position in which said cartridge holder is located at said rear end of said housing ready to cooperate with the tiring mechanism; iirst spring means engaging said outer cylinder and biased so as to yieldably maintain said outer cylinder in said extended position; second spring means engaging `said inner cylinder and biased to maintain `the latter in said idle position; a piston slidably `guided in said cylinder means, said piston having a front end adapted to engage a 'bol-t to be driven Iby said apparatus and said piston having a shoulder face engaging a. corresponding shoulder face on said inner cylinder so as to move said inner cylinder from said forward idle to said cocked position upon insertion of a :bol-t into said front end of said outer cylinder in engagement with said front end of said piston and upon exerting forward pressure on said housing; and cooperating stop means on said inner cylinder and on said housing for stopping rearward movement of said inner cylinder relative to said housing in said cocked position so that regardless of the length of the bolt inserted in said front end of said outer cylinder, said inner cylinder will always have in said cocked position the same position relative to said housing and different bolt lengths will result in different retracted positions of said outer cylinder relative to said housing.

3. An apparatus as set forth in claim 2 and including means on said outer cylinder and cooperating Iwith said housing for stopping movement of said outer cylinder into said housing at a rear end position, and wherein said rear portion of said inner cylinder projects rearwardly beyond said outer cylinder for such a length that when said outer cylinder is in said rear end position, said inner cylinder will remain forwardly of its cocked position and can be moved to said cocked position only by inserting a bolt in said front end of said outer cylinder to move thereby said piston and said inner cylinder to said cocked position of the latter.

4. An apparatus as set yforth in claim 3 wherein said means for stopping movement of said outer cylinder into said housing comprise a protective cap fastened to and surrounding said front end of said outer cylinder, said cap having a rear shoulder face adapted to engage a front face of said housing.

5. An apparatus as set forth in claim 2 wherein said front end of said piston is formed with a blind bore adapted to receive an end portion of a bolt.

6. An apparatus as set forth in' claim 2 wherein said outer cylinder has adjacent said front end `thereof a guide portion of an inner diameter smaller than the inner diameter of the remainder of said outer cylinder, and `wherein said piston has a front section of a diameter substantially equal to that of said guide portion, a shoulder section of a diameter substantially equal to that of the inner diameter of Ithe remainder -of said outer cylinder, and a main portion of a diameter substantially equal to the inner diameter of the inner cylinder.

7. An apparatus as set forth in claim 6, wherein said piston has a `rear end portion of a diameter smaller than said main portion and `wherein said cartridge holder connected to said rear portion of said inner cylinder is formed with a stepped bore having its smallest diameter at the rear end thereof substantially equal to the diameter of said rear end portion of said piston, an intermediate bore portion of a diameter substantially equal to that of said main portion of said piston and a front end portion of a diameter greater than said main portion of said piston to form a chamber around part of said main portion of said piston.

8. An apparatus as set `forth in claim 7 and including passage means providing communication `between said chamber and the interior of said housing.

9. An apparatus for driving bolts into masonry or the Ilike comprising, in combination, a housing having a rear end adapted to carry a airing mechanism; cylinder means in said housing including an -outer cylinder guided in said housing in longitudinal direction with respect thereto, slidably rearwardly from a forward position thereof, an inner cylinder having a rear end, and a cartridge holder connected to said rear end, said inner cylinder being movable together ywith said cartridge holder relative to said outer cylinder rearwardly from an idle position in which said cartridge holder is spaced a predetermined distance from the ring mechanism when said outer cylinder is in said forward position thereof; resilient means cooperating with said inner cylinder for yieldably holding the latter relative to said outer cylinder in said idle position; a piston located within and slidably guided in said cylinder means and having a front end adapted to engage a bolt to be driven by said apparatus, said piston engaging said inner `cylinder to move the latter from said idle posi- -tion rearwardly when said piston is moved rearwardly by a bolt engaging its front end; and means on said outer cylinder and cooperating with said housing to block rearward movement of said outer cylinder relative to said housing -beyond .a rear position in which said outer cylinder is rearwardly displaced from said forward position thereof a distance which is smaller than Ithe predetermined distance, so that said cartridge holder can be brought to a position ready for firing only by placing a bolt in engagement with said front end of said piston to move the latter rearwardly and thereby said inner cylinder yrearwardly from said idle position relative to said outer cylinder against the force of resilient means and by moving said outer cylinder from said forward to said rearwardly displaced position thereof.

References Cited by the Examiner UNITED STATES PATENTS 2,679,645 6/54 Erickson 1`44.5 3,050,732 8/62 Termet 1-445 3,060,436 10/62 De Caro et al. 1--44.5 3,061,833 11/62 De Caro 1-44.5

FOREIGN PATENTS 1,000,749 1/57 Germany.

GRANVILLE Y. CUSTER, JR., Primary Examiner. 

1. AN APPARATUS FOR DRIVING BOLTS INTO MASONRY OR THE LIKE COMPRISING, IN COMBINATION, A HOUSING HAVING A REAR AND ADAPTED TO CARRY A FIRING MECHANISM; CYLINDER MEANS HAVING A FRONT END AND A REAR PORTION FACING THE REAR END OF SAID HOUSING AND FORMING A CARTRIDGE HOLDER, SAID CYLINDER MEANS BEING SLIDABLY GUIDED IN SAID HOUSING BETWEEN A FORWARD IDLE POSITION AND A COCKED POSITION IN WHICH SAID CARTRIDGE HOLDER IS LOCATED AT SAID REAR END OF SAID HOUSING READY TO COOPERATE WITH THE FIRING MECHANISM; SPRING MEANS ENGAGING SAID CYLINDER MEANS AND BIASED SO AS TO YIELDABLY MAINTAIN SAID CYLINDER MEANS IN SAID IDLE POSITION SO AS TO PREVENT MOVEMENT OF SAID CYLINDER MEANS TO SAID COCKED POSITION IN THE ABSENCE OF A BOLT IN SAID FRONT END PORTION OF SAID CYLINDER MEANS; AND A PISTON SLIDABLY GUIDED IN SAID CYLINDER MEANS, SAID PISTON HAVING A FRONT END ADAPTED TO ENGAGE A BOLT TO BE DRIVEN BY SAID APPARATUS AND SAID PISTON HAVING A SHOULDER FACE ENGAGING A CORRESPONDING SHOULDER FACE ON SAID CYLINDER MEANS SO AS TO MOVE SAID CYLINDER MEANS FROM SAID IDLE TO SAID COCKED POSITION UPON INSERTION OF A BOLT INTO SAID FRONT END OF SAID CYLINDER MEANS IN ENGAGEMENT WITH SAID FRONT END OF SAID PISTON AND UPON EXERTING FORWARD PRESSURE ON SAID HOUSING. 